Electronic article surveillance (“EAS”) systems are generally known in the art for the prevention or deterrence of unauthorized removal of articles from a controlled area. In a typical EAS system, EAS tags, markers and labels (collectively “tags”) are designed to interact with an electromagnetic field located at the exits of the controlled area, such as a retail store. These EAS tags are attached to the articles to be protected. If an EAS tag is brought into the electromagnetic field or “detection zone,” the presence of the tag is detected and appropriate action is taken, such as generating an alarm. For authorized removal of the article, the EAS tag can be deactivated, removed or passed around the electromagnetic field to prevent detection by the EAS system.
Radio-frequency identification (“RFID”) systems are also generally known in the art and may be used for a number of applications, such as managing inventory, electronic access control, security systems, and automatic identification of cars on toll roads. An RFID system typically includes an RFID reader and an RFID device. The RFID reader may transmit a radio-frequency (“RF”) carrier signal to the RFID device. The RFID device may respond to the carrier signal with a data signal encoded with information stored by the RFID device.
The market need for combining EAS and RFID functions in the retail environment is rapidly emerging. Many retail stores that now have EAS for shoplifting protection rely on bar code information for inventory control. RFID offers faster and more detailed inventory control over bar coding. Retail stores already pay a considerable amount for hard tags that are re-useable. Adding RFID technology to EAS hard tags can easily pay for the added cost due to improved productivity in inventory control as well as loss prevention. Thus, the emergence of combination EAS/RFID tags.
Reusable EAS/RFID tags are typically removed from their articles before the customer exits the store. Combination EAS/RFID hard tags are affixed to their article by a clamp type mechanism. There are two types of attachment methods commonly used with combination hard tags. One is a magnetic clamp type device that uses a permanent magnet in the detacher unit to disengage the attachment pin in the combination tag for removal. The other is a mechanical spring clamp type device that uses some type of mechanical force on the attachment mechanism in the combo tag to disengage the attachment pin in the combination tag for removal. In order to remove these tags, tag detaching units are used.
Some EAS tags are removed from their articles by use of a magnetic detacher. These types of tag detaching units use strong permanent magnets to engage a magnetic type clamp located in the combination tag. These detaching units also use near field antennas to communicate with the combination tag and allow the combination tag to be rotated about the detacher magnet axis. Near field antennas could be, for example, near field UHF antennas which may be circular and may use circular meanderline geometry for use in a magnetic clamp detacher device. However, these magnetic type detaching units are ineffective with mechanical spring clamp type mechanisms used with combination hard tags.
One type of mechanical spring clamp type of tag detaching unit uses a UHF antenna to detect the combination EAS/RFID tag using a 2,450 MHz RFID element. The problem with this approach is that the wire antenna is too long to fit inside of the detaching unit housing unless it is substantially bent into almost a complete loop. It is difficult to produce an antenna of this type, the performance varies substantially with power, and it is expensive as it needs an additional 3 dB coaxial pad device for impedance matching.
Thus, there is a need for a non-magnetic detaching unit that can detach a combination EAS/RFID tag from its article.